Relay



March 28, 1939. M. R. MILLER RELAY Filed May 6, 1936 FIG. 1

FIG. 2

INVENTOR. MERTON R. MILLER BY i ATTORNEY.

Patented Mar. 28, 1939 UNITED STATES PATENT OFFICE mesne assignments,

to Associated Electric Laboratories, Inc., Chicago, 11L, a corporation of Delaware Application May 6, 1936, Serial No. 78,221-

9 Claims.

The present invention relates in general to relays, and the object of the invention is a new and improved relay characterized by the property of operating when its circuit is opened rather than when the circuit is closed. The new relay has various uses. For example, it may be used to replace the so-called two-step relays or relay combinations in common use, and it is also well adapted for use as a counting relay in counting relay chains.

The invention will be described hereinafter in 'connection with the accompanying drawing, in which Fig. 1 shows the structure of the relay, while Fig.2 is a circuit diagram showing how a plurality of such relays may be connected up to form a counting chain.

Referring to the drawing, Fig. l, the relay comprises a core 2, a heel piece 3, and an armature 5, the latter being pivoted on a bracket l attached to the heel piece. These parts may be the same as used in ordinary telephone relays. Contact springs may be mounted on heel piece 3 in known manner, but are not shown in Fig. l.

The relay has two windings l and t which are wound in opposite directions, that is, the relay is differentially wound. These windings may have the same number of turns. There is a resistance t in series with the winding i. This resistance should be non-inductive.

36 There may also be provided, although it is not strictly necessary under all conditions, an auxiliary pole piece 6. This pole piece is mounted on the core 2 at the center thereof and extends toward the heel piece 3. There is a substantial 0 air gap between the pole piece 6 and the heel piece.

When the circuit of the relay is closed at K,

current flows through windings T and B in parallel. As previously stated, the windings oppose each other. The resistance 9 may have such a iii value that the ampere turns of winding 1 arereduced to the point where this winding is nearly but not quite effective to balance the magnetizing efiect of winding 8 tending to produce flux in the magnetic circuit which includes the core 2, armature 5, and heel piece 3 in series. Thus the relay is slightly biased in favor of operation by winding 8, or by flux having the direction of that produced by winding 8 when the circuit is closed.

At the same time there is a substantial leakage flux produced by winding 8 in the magnetic circuit which includes the lower half of core 2, the

pole piece 6, and the lower part of heel piece 3.

This leakage flux may be very much greater than 55 the flux which follows the path through the armature and which may be referred to as the biasing flux. Withthe circuit closed then the winding 1 may be regarded as producing no flux and storing no energy, while winding 8 produces a small biasing flux and a considerable'leakage 5 flux, with the resultant storage of a considerable amount of energy.

When the circuit is broken at K current fiow in winding 1 immediately drops to zero, as the winding has been producing no flux. Winding 8, w however,has been producing a considerable field, especially in the leakage path which includes the pole piece t, and. the collapse of this field tends to maintain the current flow in winding 8 in the same direction. Thus a momentary current flow 5 is established in the local circuit which includes winding 8, winding l, and resistance 9 in series, and at this time the current flow in winding l is in the reverse direction from what it was when the relay circuit was closed, so that the windings l and E are now cumulative. The local circuit therefore constitutes a medium by which the energy stored in the leakage path may be converted to current and the circuit is so related to the relay structure that this induced current produces flux in the core, armature, heel piece magnetic circuit, with the result that the armature is operated.

The operation of. the relay is quite positive and its adjustment and the regulation of the value of resistance ii are not especially critical. If the value of resistance 9 is fairly high a considerable biasing flux will be produced, which assists in operating the relay when the circuit is broken, but on the other hand the resistance 9 is included in the local circuit and has the effect of reducing the induced current. When the resistance 9 is lower, so as to enable winding 8 to produce littleor no biasing flux, the low value of ren'stance 9 enables a greater induced current to to flow. The resistance 9 may therefore be varied over a considerable range without greatly afiecting the operation of the relay. It should, however, be large enough so that winding '7 cannot produce a biasing flux of reverse polarity. That is, if there is any flux through armature 5 under closed circuit condition, this flux should be due to the preponderating influence of winding 8 rather than winding 1.

An ordinary double-wound relay without any special pole piece such as 6 may be used with good results, with a heel piece such as shown in the drawing. That portion of the heel piece which extends parallel to the core lies close to the outer turns of the windings and hence is near enough to the core so that a considerable leakage flux will be produced anyway. The utility of the pole piece is that it permits a somewhat greater leakage flux to be established, and moreover the pole piece concentrates most of this flux in a magneticcircuit passing through all the turns of winding 8, whereby the maximum voltage is induced in the local circuit when the flux dies out. 7

Instead of giving the windings 1 and 3 an equal number of turns and cutting down the magnetizing eilect of winding 1 by means of an external resistance, good results can be secured by omitting the resistance and proportioning the windings so that each winding has the proper number of ampere turns to produce a balance (or slight bias in favor of winding 3) when the relay circuit is closed.

As shown in Fig. 1, the relay will operate when its circuit is opened and will fall back again, that is, it operates only momentarily. While a relay of this character is useful, there are certain situations in which the relay can be used which require that it be provided with a locking circuit so as to maintain it energized. Fig. 2 shows by way of example how a plurality of the relays can be used for a counting chain. The relays are adapted to be energized successively responsive to a series of impulses and each relay locks itself.

Referring to Fig. 2, when the key Kl is closed the line relay is energizes and at 25 closes a circuit for the slow-to-release relay 20. On energizing, relay prepares a locking groimd circuit for the counting relays 2|-24 at 28, and at 26 it prepares an impulsing circuit to the counting relays. The device CD, which is in series with line relay I9, is an automatic dial or; calling device of well known type.

It will be assumed now that the dial CD is oper-- ated in accordance with the digit 3. As a result, three interruptions are produced in the circuit of line relay l9 and the relay falls back three times. Relay 20 remains operated during the momentary deenergizations of relay l3.

The first time relay l9 falls back it sends an impulse to the first counting relay 2| over a circuit extending from ground at by way of 26, 21, and the two windings of relay 2| in parallel to battery. The circuit of the upper winding of the relay includes the resistance 3|. As already explained, the relay does not operate while its circuit is closed but at the end of the impulse, when the circuit is broken at 25, the relay operates by induced current in the local circuit which includes the two windings in series and resistance 3|. The contact29-30 is preferably adjusted to close first and completes a locking circuit from ground at 23 by way of 29, 3D, and the upper and lower relay windings in series to battery. At the same time the local circuit is broken at 3|). It will be noted that the two windings are connected cumulatively in the locking circuit, the same as they were in the local circuit, with the direction of current flow the same. The locking circuit may be relied on to quickly complete the energize.- tion of the relay and enables a heavy spring load to be carried.

At 21 the first counting relay 2| transfers the impulsing circuit to the second counting relay 22, so that on the second deenergization of line relay IS an impulse is transmitted to relay 22. Relay 22 responds like relay 2 energizing at the end of the impulse, and locks itself at 32. Relay 22 also transfers the impulsing circuit at 33.

On the last deenergization of the line relay l3,

an impulse is transmitted to counting relay 23, which locks itself at 34. Relay 23 also transfers the impulsing circuit at but no more impulses are received and the apparatus comes to rest with the three relays 2|, 22, and 23 in energized condition, as well as relays l9 and 20. It will be clear that if the digit 4 had been dialled, then iour counting relays would have been successively energized, and so on. Although only four counting relays are shown, the chain may obviouslybe extended to include ten, or any desired number.

When the key Kl is restored the line relay l3 deenergizes, followed after an instant by the release relay 20. On the deenergization of the line relay an impulse is, of course, transmitted to the fourth counting relay 24 and this relay will attempt to lock itself when the impulsing circuit is broken at 26 by the falling back of relay 20. Re-

- lay 20, however, opens the locking circuits of all the counting relays at 28 and they all restore to normal.

The invention having been described, what is considered to be new and is desired to have protected by Letters Patent is set forth in the following claims.

What is claimed is:

1. In a relay, a magnetic structure and two similar differential windings which prevent the relay from operating its armature when the relay circuit is closed, said windings and structure so related as to cause the relay to operate its armature by generation of a flux in said structure when said circuit is broken.

2. In a relay, two windings connected in opposition, whereby the relay is not operated when its circuit is closed; a magnetic structure enabling one winding to produce leakage flux, and means including both windings for operating the relay responsive to the decay of leakage flux when the relay circuit is broken.

3. In combination, a relay, two windings, a circuit for energizing said windings in parallel opposition connection, the relay armature being non-responsive, a local circuit including said windings in cumulative series connection, and a magnetic structure such that current flow is produced in said local circuit to operate the relay armature when said first circuit is broken.

4. In combination, a relay, a winding on said relay, a second winding operative to prevent said first winding from operating the relay armature when energized, a path for leakage flux produced by said first winding, said path excluding the relay armature, a circuit for energizing said windings, and means including both windings for utilizing the decay of leakage flux when said circuit is broken to drive flux through the armature and operate the same.

5. In combination, a relay including a core, a heel piece, and an armature, a magnetic circuit including said elements, a second magnetic circuit including a portion of said core and a portion of said heel piece but excluding said armature, two windings on said relay, and circuit connections for said windings such that when the windings are energized from an external source of current flux is produced in the second circuit but substantially none in the first circuit and whereby when said source is disconnected the said windings constitute means for utilizing the decay of flux in the second circuit to produce flux in the first circuit.

6. In combination, a relay having two windings, a circuit in which said windings are connected in parallel opposition, said windings having an unequal number or ampere turns when energized in said circuit, a path for ieakage flux produced by the more powerful winding, a local circuit including said windings connected cumulatively in series in which current is induced by the collapse of the leakage flux upon opening said first circuit, and an armature for the relay which is in the same direction as the induced current in said second circuit.

8. A relay comprising-a magnetic structure, difierential windings, a circuit including said windings, a source of current, means for connecting said source to said circuit, said circuit preventing the relay from operating its armature when said circuit is energized said windings so connected as to cause the relay to operate its armature when said circuit is deenergized.

9. A relay, a magnetic structure, diflerential windings connected in a closed circuit which prevent the relay from operating its armature when an electromotive force is applied across said circuit said windings so connected-in said closed circuit as to cause the relay to operate its armature when said force is removed.

MERTON R. MILLER. 

